Temperature range extension for electric compressor

1 . An electric compressor comprising:

an electric motor including a rotor and stator and a shaft rotating with the rotor to drive a compressor impeller;

bearings supporting the shaft;

a housing enclosing the shaft, the bearings and the electric motor, and a sensor for sensing a condition within the housing;

a control for the electric motor receiving information from the sensor indicative of the potential of migrated refrigerant when the electric motor is not running, and the control being operable to actuate a countermeasure to deliver heat into the housing to boil off the migrated refrigerant; and

wherein at least one of the following is true:

wherein the bearings are magnetic bearings and the countermeasure is to actuate the magnetic bearings when the electric motor is not running; and/or

wherein the countermeasure is the electric motor being controlled to generate heat while the system is idle, the countermeasure is running the electric motor at a low speed so as to act as a heat source when the system is idle, and a check valve is positioned downstream of the compressor impeller, and opens when the compressor impeller pressurizes a refrigerant to a sufficient pressure, and the low speed is defined as running the electric motor such that the compressor impeller will not pressurize the refrigerant enough to open the check valve; and/or

wherein the countermeasure is the rotor being provided with an electric brake so as to act as a heat source when the system is idle, wherein the electric motor is an AC motor, and the electric brake is controlled by supplying a DC voltage to the electric motor.

2 . The electric compressor as set forth in claim 1 , wherein the bearings are magnetic bearings and the countermeasure is to actuate the magnetic bearings when the electric motor is not running.

3 . The electric compressor as set forth in claim 1 , wherein the countermeasure is the electric motor being controlled to generate heat while the system is idle.

4 . The electrical compressor as set forth in claim 3 , the countermeasure is running the electric motor at the low speed so as to act as the heat source, when the system is idle.

5 . The electric compressor as set forth in claim 4 , wherein the check valve is positioned downstream of the compressor impeller, and opens when the compressor impeller pressurizes the refrigerant to the sufficient pressure, and the low speed is defined as running the electric motor such that the compressor impeller will not pressurize the refrigerant enough to open the check valve.

6 . The electrical compressor as set forth in claim 3 , wherein the countermeasure is the rotor is provided with the electric brake so as to act as the heat source, when the system is idle.

7 . The electric compressor as set forth in claim 6 , wherein the electric motor is the AC motor, and the electric brake is controlled by supplying the DC voltage to the electric motor.

8 . The electric compressor as set forth in claim 1 , wherein the countermeasure is actuated at least thirty seconds before an intended startup of the electric compressor.

9 . The electric compressor as set forth in claim 1 , wherein the countermeasure is cycled on and off.

10 . The electric compressor as set forth in claim 1 , wherein the countermeasure is disabled if a threshold temperature is reached within the electrical compressor.

11 . A method of operating a compressor comprising the steps of:

determining that an electric motor for a compressor is not driving an impeller for the compressor;

evaluating conditions within the housing to determine if they are indicative of the likely presence of migrated refrigerant when the electric motor is not driving the impeller; and

taking a countermeasure to boil off the migrated refrigerant within the housing, and while the electric motor is not driving the impeller;

wherein at least one of the following is true:

the countermeasure is actuating magnetic bearings when the electric motor is not running; and/or

the countermeasure is the electric motor being controlled to generate heat while the system is idle by running the electric motor at a low speed so as to act as a heat source, when the system is idle, and a check valve positioned downstream of the compressor impeller, and opens when the compressor impeller pressurizes a refrigerant to a sufficient pressure, and the low speed is defined as running the electric motor such that the compressor impeller will not pressurize the refrigerant enough to open the check valve; and/or

the countermeasure is a rotor provided with an electric brake actuated when the system is idle, wherein the electric motor is an AC motor, and the electric brake is controlled by supplying a DC voltage to the electric motor.

12 . The method as set forth in claim 11 , wherein the electric motor includes the rotor driving a shaft to in turn drive the impeller, and the shaft is supported on the magnetic bearings, and the countermeasure includes actuating the magnetic bearings to deliver heat into the housing when the electric motor is not driving the impeller.

13 . The method as set forth in claim 11 , wherein the electric motor includes a rotor provided with the electric brake, and the countermeasure includes actuating the electric brake while the electric motor is not driving the impeller.

14 . The method as set forth in claim 13 , wherein the electric motor is the AC motor, and the countermeasure is the electric brake is controlled by supplying the DC voltage to the electric motor.

15 . The method as set forth in claim 14 , wherein the countermeasure is actuated at least thirty seconds before an intended startup of the electric compressor.

16 . The method as set forth in claim 11 , wherein the countermeasure running the electric motor at low speed.

17 . The method as set forth in claim 16 , wherein the check valve is positioned downstream of the compressor impeller, and opens when the compressor impeller pressurizes the refrigerant to the sufficient pressure, and the low speed is defined as running the electric motor such that the compressor impeller will not pressurize the refrigerant enough to open the check valve.

18 . The method as set forth in claim 11 , wherein the countermeasure is actuated at least thirty seconds before an intended startup of the electric compressor.

19 . The method as set forth in claim 11 , wherein the countermeasure is cycled on and off.

20 . The method as set forth in claim 11 , wherein the countermeasure is disabled if a threshold temperature is reached within the electrical compressor.